Yarn traversing apparatus



May 14, 1963 P. J. CHAUSSY YARN TRAVERSING APPARATUS 2 Sheets-Sheet 1Filed Jan. 5, 1961 FIG.

FIG?) May 14, 1963 Filed Jan. 5, 1961 P.- J. CHAUSSY YARN TRAVERSINGAPPARATUS 2 Sheets-Sheet 2 United States Patent This invention relatesgenerally to the traverse winding of yarn at high speeds and moreparticularly to improvements in the cam. which is an integral part ofthe Winding apparatus.

It is well known in the textile field to wind substantially cylindricalpackages of yarn, thread or the like on a bobbin in a traverse windingapparatus. In such an apparatus the yarn passes through a reciprocatingguide to a rotating package. The guide is attached to a follower whichrides in a generally helical groove in the surface of a rotatably drivenbarrel cam and is constrained to follow a reciprocating linear path oftravel. An apparatus of this type has been disclosed by Hunter in US.Patent No. 2,689,694. Although such an apparatus is entirely suitablefor use at the speeds contemplated, it has been found that higherwinding speeds lead to the formation of unstable packages having bulgedend faces and overthrown ends. These unacceptable results are caused bythe reduction in follower velocity in the circular reversal portion ofthe cam profile and the concurrent deposit of surplus yarn at thepackage ends. In the past, it has been thought that a relatively sharp,angular reversal portion in the cam profile would eliminate the buildupof shoulders. Actually, the shoulders still appear. Furthermore, such aremedy is unpracticable because of the high acceleration forces actingon the follower and guide, i.e., the nearly instantaneous change indirection subjects the follower to excessive acceleration and loads.

The principal object of the present invention is to provide cam profileimprovements which facilitate the formation at high winding speeds ofstable, substantially cylindrical, uniformly dense yarn packages havingflat end faces.

A corollary objective is the provision of a cam profile whichfacilitates high speed winding without subjecting the cam and followerto excessive loads at the cam reversal points.

These and other desirable objectives are accomplished in a Windingapparatus which includes a rotatably driven barrel cam having acontinuous, generally helical groove in its surface, a cam followerriding in the groove and guide rails limiting the follower to areciprocating linear path of travel between the cam reversal points. Asuitable yarn guide is attached to the follower for movement therewith.The cam groove is characterized by successive straight, cycloidal,harmonic, cycloidal and straight portions in its profile at the reversalpoints.

Other objectives will become apparent in the following specificationwherein reference is made to the accompanying drawings in which:

FIGURE 1 is a partial elevational view of a traverse winding apparatusinto which the improvement of the present invention may be incorporated;

FIG. 2 is a cam profile having harmonic curves at the reversal points;

FIG. 3 illustrates the package outline which results when the camprofile of FIG. 2 is employed;

FIG. 4 illustrates the theoretical Package outline corresponding to theprofile of FIG. 2;

FIG. 5 is the cam profile of the present invention;

FIG. 6 shows the actual package formation resulting when the cam profileof FIG. 5 is employed;

FIG. 7 is the theoretical package outline corresponding to the profileof FIG. 5;

FIG. 8 is an enlarged diagram of one of the reversal points shown in theprofile of FIG. 5; and

FIG. 9 is a top plan view of a barrel cam having a groove correspondingto the profile of FIGS. 5 and 8.

The winding apparatus chosen for purposes of illustration in FIG. 1includes as components thereof a rotatably driven barrel cam 10 having agroove 12 in its cylindrical surface and a follower 14 having a yarnguide attached thereto which follower rides in groove 12 and isconstrained to a linear path of travel by rails 16, 18.

The magnitude of the acceleration forces imposed on a cam follower is afunction of the radius of the reversal curves with the practical minimumradius being limited by the ability of the follower to withstand highinertial forces. It is known that traverse cams with sharp constantvelocity reversal patterns subject the follower to instantaneousacceleration shocks. Where the reversal pattern is circular, the shocksare not instantaneous but are nevertheless abrupt.

A cam profile having harmonic reversal curves has been designated withthe numeral 20 in FIG. 2. When such a profile is milled into a cam ofthe type shown in FIG. 1, it produces gradual acceleration changes andis accordingly ideally suited for use in a high speed apparatus. Evenwith such gradual acceleration changes, there is still a deposit on thepackage of surplus yarn or shoulders 22 (FIG. 4) opposite the reversalpoints. The pressing action of a drive rol-l (not shown) which is infrictional contact with the package surface assists in redistributingthe yarn from the theoretical outline shown in FIG. 4 to the actualthough exaggerated saddle back shape shown r in FIG. 3.

In FIGS. 5 and 8 the preferred cam profile of the present invention isshown and has been designated with the numeral 24. Profile 24 includesstraight portions 26, harmonic reversal curves 28, and intermediatecycloidal curve portions 30. In each portion 30, there is a change ofcam direction or slope which results in a gradual acceleration of thefollower as it leaves a straight portion 26 and a gradual decelerationas it leaves a harmonic curve 28. In the actual reversal portion 28 fulladvantage is taken of the gradual acceleration characteristics of aharmonic curve as discussed above in connection with FIGS. 2-4. Thestroke limit or reversal point for follower 14 is at the mid-point ofharmonic curve 28. The overall increase in velocity in the approach toand departure from the reversal point leads to a theoretical cutback 32(FIG. 7) near the ends of the package. In actual practice, surplus yarnshoulders 22 corresponding to harmonic curves 28 slip into the lowdensity regions or cutbacks 32 corresponding to cycloidal curves 30. Thepressing action of the package drive roll assists in this redistributionof yarn. Cutbacks 32 disappear and the package faces are flat, asindicated at 33. Since cutbacks 32 result from an increase in followervelocity in the cycloidal portions 30 of profile 24, portions 30 arealso referred to as cutbacks in the profile. The apparatus shown in FIG.9 has a cam groove 12' corresponding to the profile of FIG. 8 but isotherwise identical to the apparatus of FIG. 1.

Although the cutback portions 30 of the preferred profile are cycloidal,it is practicable and sometimes advantageous to use other curves ofvarying radius, e.g., polynomials, as the junctures between the straightand harmonic curve portions. The principal requirement is that theacceleration characteristics at both ends of the transitional or cutbackcurve blend with the acceleration characteristics of the adjacentcurves.

As is apparent from the tangent lines shown in FIG.

8, the cutback portions 39 join constant velocity portions 26 andharmonic portion28 atpoints of zero acceleration. Thus, the follower 14enters a cutback portion 30 at constant velocity, accelerates to somefinite value and leaves the cutback portion at zero acceleration. Thetransition is continuous and smooth with no sudden or large changes inacceleration.

With reference to FIG. 8 it should be noted that the maximum pressureangle 99 for the profile of this invention exceeds the normal pressureangle or cam helix angle 88 by the size of the cutback angle 77.Previous cam profiles have not included a definite cutback angle 77.

Substantially cylindrical packages of heavy industrial yarn have beenwound at high speeds using a cam having a cutback angle 77 as large as13, a helix or normal pressure angle 88 of about 30, and a maximum ortotal pressure angle 99 of over 40. Similarly, a cutback angle of aslittle as 4 with a cam helix angle of about 30 is suitable for lightertextile counts. Between these two extremes cutback angles of from 4-13have been used successfully in the winding of various nylon, polyester,and spandex fiber counts at windup rates approaching 5,000 yards perminute.

Although the preceding description relates primarily to the use ofbarrel cams, it is apparent that the concept of adding a cutback portionto a cam profile is equally applicable to plate and other type cams.Additional changes to and adaptations of the disclosed cam profile maybe made without departing from the spirit of the present invention whichis accordingly intended to be limited only by the scope of the appendedclaims.

I claim:

1. A winding apparatus including a rotatably driven barrel cam having acontinuous generally helical groove in its surface, a cam followerriding in said groove and means limiting the follower to a reciprocatinglinear path of travel between the cam reversal points, said followerhaving a guide fixedly attached thereto and said groove having a profileincluding successive straight, cutback curve, reversal curve, cutbackcurve and straight portions, said profile being entirely curvilinear inthe portions interconnecting said straight portions, said cutback curvesbeing respectively curves of gradual acceleration and deceleration, eachreversal curve having gradual deceleration and accelerationcharacteristics respectively in the approach to and departure from saidreversal points.

2. The apparatus of claim 1 wherein said cutback curve portions arecycloidal.

3. The apparatus of claim 1 wherein the cutback angle is at least 4.

4. The apparatus of claim 1 wherein the maximum pressure angle is inexcess of 30 and the cutback angle is at least 4.

References Cited in the file of this patent UNITED STATES PATENTS1,357,434 Anderson Nov. 2, 1920 2,858,993 Siegenthaler Nov. 4, 19582,934,284 Steeger Apr. 26, 1960 2,959,967 Metzuer Nov. 15, 1960 FOREIGNPATENTS 1,054,337 France Oct. 7, 1953

1. A WINDING APPARATUS INCLUDING A ROTATABLY DRIVEN BARREL CAM HAVING ACONTINUOUS GENERALLY HELICAL GROOVE IN ITS SURFACE, A CAM FOLLOWERRIDING IN SAID GROOVE AND MEANS LIMITING THE FOLLOWER TO A RECIPROCATINGLINEAR PATH OF TRAVEL BETWEEN THE CAM REVERSAL POINTS, SAID FOLLOWERHAVING A GUIDE FIXEDLY ATTACHED THERETO AND SAID GROOVE HAVING A PROFILEINCLUDING SUCCESSIVE STRAIGHT, CUTBACK CURVE, REVERSAL CURVE, CUTBACKCURVE AND STRAIGHT PORTIONS, SAID PROFILE BEING ENTIRELY CURVILINEAR INTHE PORTIONS INTERCONNECTING SAID STRAIGHT PORTIONS, SAID CUTBACK CURVESBEING RESPECTIVELY CURVES OF GRADUAL ACCELERATION AND DECELERATION, EACHREVERSAL CURVE HAVING GRADUAL DECELERATION AND ACCELERATIONCHARACTERISTICS RESPECTIVELY IN THE APPROACH TO AND DEPARTURE FROM SAIDREVERSAL POINTS.